Mysterious sci-fi ships

• Subject of a museum in Roswell, New Mexico
• Pies in the sky?
• Strange saucers
• Conspiracy subjects
• "X-Files" topics
• Subjects of sightings
• Abduction vehicles, supposedly
• They're encountered in "close encounters"
• Alien spaceships: Abbr

Wiktionary Word definitions in Wiktionary
n. (plural of ufo English)